1. Field of the Invention
The present invention relates to the fabrication of integrated circuits and, more particularly, to the technology for improving large-scale integration semiconductor performance through diagonal routing.
2. Description of the Prior Art
As known in the art, a chip's microscopic transistors are ordinarily wired together on a grid of right-angle interconnects—known, in fact, as “Manhattan routing” for their resemblance to city streets. When one electron path needs to cross another, it must first shift up or down to another wiring layer via a Z-axis interconnect—known, in fact, as a via.
Chipmakers have jumped technical hurdles and worked wonders to create smaller chips and shorter interconnects—moving from 0.18- to 0.13-micron to 90-nanometer process manufacturing. They have toiled to raise speed limits or grease the paths—moving from aluminum to copper to silicon-on-insulator (SOI), strained-silicon, and low-k-dielectric designs. But they are still taking the long way around—tracing the legs of a right triangle instead of the hypotenuse.
In traditional Manhattan architecture, each metal routing layer has a fixed direction in which the wires can be drawn. This is called the “preferred direction.” The first layer has horizontal routing, and the subsequent layers have alternating vertical and horizontal routing. While there are automatic routing tools for printed circuit boards that can draw wires diagonally, these have not been used in chip design. This is because chip routing is far more complex, with huge numbers of elements integrated, in comparison to printed circuit board routing.
Since 2001, a consortium of processor and production-equipment makers (also known as “the X Initiative”) has been determined to overcome this fundamental limitation—to give chip designers the choice of diagonal as well as horizontal and vertical wires or interconnects. They call this concept the X Architecture, and the chip using the X Architecture routing method—the X chip. Compared to a Manhattan version of the same design, the X chip required less wire length and fewer vias, hence lower manufacturing cost. However, there are still some obstacles to be overcome in order to obtain better performance of an integrated circuit (IC) routed by the X Architecture.